1. Field of the Invention
The present invention relates to a stacked mounting structure, and particularly to a three-dimensional stacked mounting structure which is made by stacking a plurality of members in a direction of thickness of the members.
2. Description of the Related Art
Regarding a structure which includes a substrate on which electronic components are mounted, various structures have hitherto been proposed (refer to Japanese Patent Application koukoku (post-exam. publn.) No. Hei 4-38417 and Japanese Patent Application Laid-open Publication No. Hei 11-111914 for example). In Japanese Patent Application koukoku (post-exam. publn.) No. Hei 4-38417, for example, as shown in FIG. 8, a mounted structure related to an image pickup unit which is provided at a front-end portion of an endoscope 10 has been disclosed. Here, a technology of stacking a mounting substrate parallel to an image pickup element 11 has been described. In this technology, first of all, a mounting substrate 12 is disposed parallel to the image pickup element 11. Next, the mounting substrate 12 on which the image pickup element 11 is mounted, and a mounting substrate 13 on which the other components are mounted are mounted via a spacer. Accordingly, mounting components on the mounting substrate can be disposed in a space which is secured by a portion of a height of the spacer. Consequently, it is possible to improve a mounting density of the mounting structure. As a result of this, it is possible to facilitate making small a size of the image pickup unit which is provided at the front-end portion of the endoscope.
Moreover, in Japanese Patent Application Laid-open Publication No. Hei 11-111914, as shown in FIG. 9, a structure of a mounting structure 20 which includes a memory module substrate 24 has been disclosed. An inner side of substrates 21 facing is hollow. A plurality of electrodes is provided on both surfaces of the substrate 21. Moreover, an electrode on a front surface of the substrate 21 and an electrode on a rear surface of the substrate 21 facing are mutually connected electrically. At a connecting portion of the electrodes, an anisotropic electroconductive film 22 is attached. In this manner, in Japanese Patent Application Laid-open Publication No. Hei 11-111914, a mounting structure of the substrate 21 on which an electronic component 23 is mounted has been disclosed. In this structure, for joining an electroconductive spacer 25 and the anisotropic electroconductive film 22, an electrode is provided in a through hole which is provided in the electroconductive spacer 25.
In the structure disclosed in Japanese Patent Application koukoku (post-exam. publn.) No. Hei 4-38417, an electrical conduction between substrates disposed by stacking is secured by a lead wire 14. An automation of a job of joining the substrates by the lead wire 14 is difficult. For example, in a small structure, a job of disposing short lead wires and soldering cannot be dealt with by a normal automatic mounting machine.
Therefore, the job of fixing the lead wire 14 has to be carried out manually. Moreover, even by the manual job, such a mounting is a job in a category of a high degree of difficulty. A technology in which the automation is difficult and the degree of difficulty of the job is high, leads to an increase in a mounting cost and a decline in productivity. Moreover, when a size of the lead wire which can be handled manually, and a controllable gap between the lead wires at the time of handling are taken into consideration, the structure according to the conventional technology is disadvantageous for making small the mounting structure.
Moreover, in the structure disclosed in Japanese Patent Application Laid-open Publication No. Hei 11-111914, as it is evident from FIG. 9, it is necessary to provide an electrode of an area larger than an outer shape of the through hole, on the electroconductive spacer 25. Therefore, narrowing of a pitch of joining portions becomes difficult. In other words, it is difficult to make small a projected area when the mounting structure is viewed from a top. Moreover, in this structure, the anisotropic electroconductive film 22 is used as a material joining the electroconductive spacer 25 and the substrate 21. Therefore, there is a drawback that a resistance of connection between the electroconductive spacer 25 and the substrate 21 becomes high.
In this manner, in a case of the mounting structure of the conventional technology, it is difficult to secure a favorable productivity in making a stacked mounting of substrates via a spacer for securing a mounting space for electronic components. Moreover, it is also difficult to make the size small to reduce a projected area in a direction of a plane of a substrate.